Electronic memory cards enabling their owners to perform certain kinds of transaction are well known. There are two broad categories of such cards. Some cards have an electronic circuit which is sufficiently complex to enable credit data to be reloaded into the card memory. In other words, once the initial credit in the card has been spent, the user can have the card "reloaded" with a new amount of credit in return for suitable payment. A second or "prepaid" type of card contains a simpler electronic circuit and the card is loaded once only with a given amount of credit. Once this credit has been spent by the user, the card must be thrown away.
Since prepaid cards are used once only, it will be understood that they must be as cheap as possible to manufacture in order to avoid the cost of the card being excessive in relation to the necessarily small amount of credit which it is capable of storing. Low cost is achieved, in part, by the electronic circuit itself being considerably cheaper than the circuit used in a re-loadable card. However, the cost of manufacturing the card itself is a non-negligible quantity in the final cost of the card. Such a card is essentially constituted by a body made of plastic material, and an electronic module lodged therein, said module comprising the integrated circuit, contact tabs for providing connection with a card reader, and electrical connections between the integrated circuit and the contact tabs. The electronic module is fixed in the body of the card in a manner which is capable of ensuring that the resulting assembly can pass bending tests to which the card is subjected. In addition, the thickness of the card it standardized and this thickness is about one millimeter. It will be understood that this small thickness increases the difficulty of installing and fixing an electronic module in the card.
Various methods of implanting the electronic module in the body of the card have already been proposed. In a first method, the electronic module is placed between two layers of plastic material which constitute the card body, and the assembly is thermocompressed in order to obtain the final card shape, with the integrated circuit being buried in the body of the card.
In another method, a prefabricated card body is taken and a cavity is machined therein to receive the electronic module which is held in place by glue. Such a technique is very difficult to perform since the machining must be performed with high accuracy in order to ensure that the contact terminals of the electronic module are level with the surface of the card body after the module has been placed in the cavity.
In order to remedy these drawbacks, European patent application No. 128 822 proposes a method of implanting an electronic module in the body of the card by providing a cavity in the card body with the cavity being smaller than the outside dimensions of the electronic module, the body of the card is then locally heated while the electronic module is pressed against the card body so that at least a portion of the electronic module serves as a punch which defines parts of the card cavity. Partial melting of the plastic material making up the card body provides very secure anchoring of the electronic module in the card body and in addition avoids any need for accurate machining of the body.
In order to further improve the implantation of the electronic module in the card, preferred implementations of the present invention provide a method of implanting the electronic module in the body of the card which does not require the body of the card to be machined to accurate dimensions, while still making it easy to control card deformation during the implantation of the electronic module therein.